This invention relates generally to the manipulation of images on a computer screen, and more particularly to methods for scaling, distorting, deleting or otherwise altering the image of an object on the screen of a pen-based computer system.
Computerized personal organizers are becoming increasingly popular with a large segment of the population. Computerized personal organizers tend to be small, lightweight, and relatively inexpensive, and can perform such functions as keeping a calendar, an address and telephone book, a to-do list, etc. While many of these functions can also be provided in conventional computer systems, personal organizers are very well suited to the personal organization task due to their small size and portability. Personal organizers are available from such companies as Sharp and Casio of Japan.
A relatively new form of computer, the pen-based computer system, holds forth the promise of a marriage of the power of a general purpose computer with the functionality and small size of a personal organizer. A pen-based computer system is typically a small, hand-held computer where the primary method for inputting data includes a "pen" or stylus. A pen-based computer system is commonly housed in a generally rectangular enclosure, and has a dual-function display assembly providing a viewing screen along one of the planar sides of the enclosure. The dual-function display assembly serves as both an input device and an output device. When operating as an input device, the display assembly senses the position of the tip of a stylus on the viewing screen and provides this positional information to the computer's central processing unit (CPU). Some display assemblies can also sense the pressure of the stylus on the screen to provide further information to the CPU. When operating as an output device, the display assembly presents computer-generated images on the screen.
The dual-function display assemblies of pen-based computer systems permit users to operate the computer as a computerized notepad. For example, graphical images can be input into the pen-based computer by merely moving the stylus on the surface of the screen. As the CPU senses the position and movement of the stylus, it generates a corresponding image on the screen to create the illusion that the stylus is drawing the image directly upon the screen, i.e. that the stylus is "inking" an image on the screen. With suitable recognition software, text and numeric information can also be entered into the pen-based computer system in a similar fashion.
In the prior art, it has not been possible to manipulate or edit "inked" objects. Inked objects that have been "recognized" and displayed in a cleaned-up form can be manipulated in a straight-forward fashion because the nature of the recognized object is well understood. However, it would be desirable to be able to perform certain types of manipulation on a non-recognized object, i.e. directly on an inked object. For example, it would be desirable to be able to scale an inked object upwardly or downwardly in size, distort sides of an inked object, and delete portions of an inked object without going through a recognition routine and without replacing the inked object with a recognized version of the object.